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<html lang="en">

<head>
    <meta charset="UTF-8">
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    <title>Document</title>
</head>

<body>
    <h1>- 运算符</h1>
    <p id="demo"></p>
    <script>
        var x = 7;
        var y = 8;
        var z = x - y;
        document.getElementById("demo").innerHTML = z;
    </script>
</body>

</html>